At&t Bell Laboratories

Lucent Technologies Inc.

Avaya Technology LLC

Other

At+t Corp.

Bell Telephone Laboratories

At&t Bell Labs

Douglas A Spencer

Charles Y Farwell

Michel L Hearn

Kelvin K Ho

Richard M Heidebrecht

Norman W Petty

John S Thompson

Alan S Mulberg

Michael A Smith

David M Kissel

Michael J English

Richard Alan Windhausen

Kenneth Wayne Strom

Kenneth Frank Smolik

Richard D Miller

Paul E Miller

Talmage P Bursh, Jr

Brian D Bolliger

LaJeana N Roberts

Joel M Ezell

James A Davis

Rolfe E Buhrke

Kenneth Yiu-Kwong Ho

Tore L Christensen

Dwight W Kohs

Philip W Hartmann

Jerome J Zelenski

Steven J Szymanski

John S Helton

Garry V Turnbow

Marc K Dennison

Michael L Hearn

Jeffrey A Williams

Ernest J Frey

Wayne A Zakowski

Gail L Haygood

Providing a systematic and comprehensive mechanism for applying echo cancellation within a telecommunication switching system by a local switching system such as a PBX. Echo cancellation circuits are deployed throughout the telecommunication switching system using different types of echo cancellation circuits with each type having different capabilities with respect to a time offset of an echo return signal relative to when an voice signal was generated by a talker. The echo cancellation circuits deployed within the local telecommunication switch are an integral part of trunk circuits and provide the largest time offset. Further, the echo cancellation circuits deployed within in the local telecommunication switch are capable of controlling echoes in either direction with respect to the integral trunk circuit and may be used as service circuits if not needed by the integral trunk circuit. A systematic and comprehensive mechanism further comprises terminating echoes at the edges of networks having long transmission delays such as a wide area network (WAN) comprising a combination of ATM and/or IP switching networks. The mechanism enables uniformity in policing echoes at the 'near end' at the appropriate points in the PBX network or in a network of PBX's.

Comprehensive echo control system

allowing a central business communication system to handle all aspects of call setup on a remote switch. Call control for a telecommunication call set up on a remote switch continues to be handled by the central business communication system; however, the switching of the bearer channels is performed automatically on the remote switch if the telecommunication call is between telecommunication terminals on the remote switch. In addition, if the telecommunication call is between two remote switches, the remote switches will automatically communicate the bearer channels through an interconnecting media without going through the central business communication system. In addition, when an Internet protocol (IP) such as IETF RFC 791 is utilized to communicate the bearer channels between the central business communication system and the remote switch, multi-frequency dialing tones received from analog telephones connected to the remote switching network are converted to digital information before transmission via the IP communication channels to the central business telecommunication system.

Integration of remote access and service

Port networks (PN 101-103) of a switching system such as a distributed PBX are remoted from and interconnected with each other by an ATM network (100). Each port network includes a port network connectivity (PNC) circuit (113-114) that interfaces it to the ATM network. Only one of the port networks (101) has a system processing element (SPE 111), which controls all of the port networks. Commands issued by the SPE and needed by the ATM network to establish virtual circuits between the port networks are translated (FIG. 2) by a PNC circuit (113) into ATM signaling cells. Commands issued by the SPE and not needed by the ATM network are encapsulated (FIGS. 2 and 3) as payload into ATM traffic cells by the PNC circuit and are sent to destination processor networks through the virtual circuits. At a destination processor network, the encapsulated commands are retrieved (FIGS. 2 and 3) and used for local control. The destination processor networks function as if they were connected directly to the SPE without intermediacy of the ATM network.

Switch distribution via an intermediary switching network

A port circuit (108) for a time-division multiplexed (TDM) switching system (100) is designed to effect sub-time-slot operation without external support, as well as to effect conventional, time-slot operation. A clock-frequency multiplier, such as a frequency-multiplexed phase-lock loop (PLL 202), and a multiplier-driven sub-time-slot operation circuit, such as a PLL-driven finite state machine (203), are incorporated into the port circuit. The clock-frequency multiplier and the sub-time-slot operation circuit generate all the additional control signals that are necessary to define sub-time slots and to effect multiple information transfers in a single time slot. The port circuit engages in conventional time-slot transfers with conventional port circuits, whereby it is compatible therewith, and engages in sub-time-slot transfers with other sub-time-slot enabled port circuits, whereby it increases the transfer throughput of the TDM switching fabric. The sub-time-slot operation is selectively enabled and disabled on a per-time-slot basis.

Hybrid time-slot and sub-time-slot operation in a time-division

A port system interfaces digital PBX's to any transmission facility having DSX-1 communications ports via a microprocessor controlled PBX port board connected between PBX switch fabric and a first DSX-1 communications port. A channel service unit (CSU) module coupled directly to the port board for communications with DS1 transmission lines defines a second DSX-1 communications port which is coupled to the first DSX-1 communications port. The CSU module also includes a T1 transceiver and line interface circuitry for coupling the CSU module to a DS1 transmission line. The combination of the port board and CSU module provide full functionality of conventional CSU's while the port board alone permits direct coupling of transmission facilities utilizing a DSX-1 communications port. For remote maintenance, a microprocessor of the port board is coupled to a control processor of a PBX for control of the port board microprocessor via the PBX control processor. Wiring test circuitry is provided in the CSU module to detect faults in the wiring between a CSU module and a DS1 transmission line. The CSU module includes a transmitter transformer having a center-tapped secondary winding and a receiver transformer having a center-tapped primary winding. A current limited current source is selectively connected between the center taps of the transmitter and receiver transformers such that, when connected, one or more transformers in a CSU/DS1 interface circuit which is faulty will saturate leading to failure of transmission tests and hence proper detection of the fault.

Port system for interfacing digital PBX to digital transmission facility

A wireless-access communications system, such as a CDMA cellular radio-telephone system (FIG. 2), comprises a packet-switched communications network (202, 207, 201) that interconnects cells (base stations; 202) with each other and with the public telephone network (100). Traffic of individual calls is packetized, and packet-bearing frames (300 in FIG. 7) of a plurality of calls are then statistically multiplexed and frame-relayed through the network to yield the high capacity, efficiency, and speed of traffic transport and handoff required for a CDMA cellular system. At each call processing unit (264 in FIG. 5), individual calls are handled by individual service circuits (602 & 612) which perform speech-processing functions such as coding and decoding, tone insertion, and echo cancellation, and packet-to-circuit-switched-PCM traffic conversion. Processors (602) adapt call processing unit timing to compensate for asynchrony between cells and call processing units and variations in call path transmission delays. Cell-to-cell communications, fixed call path addressing, and packetized control message transfers ensure that the same service circuit handles a call through even multiple soft handoffs (FIGS. 27-29) and efficiently communicates simultaneously with all cells involved in the handoff without involvement of system control entities and negative effect on system call-handling capacity. Both coded (packet-switched) and uncoded (circuit-switched) radio-telephone traffic are accommodated side-by-side. Wherever possible, existing and proven technology and component units are used to achieve low cost and high reliability.

Wireless access telephone-to-telephone network interface architecture

A CDMA cellular radio-telephone system (FIG. 2) comprises a packet-switched communications network (202, 207, 201) that interconnects cells (base stations; 202) with each other and with the public telephone network (100). A unique combination of a static addressing plan that uses a different LAPD DLCI (302 in FIG. 7) for each unidirectional virtual call path, direct cell (202)-to-cell and cell-to-call-processing unit (264 in FIG. 5) control information exchanges, and packet-switching techniques that permit call traffic and control communications to share call paths and permit different call paths to share physical resources, is applied to call processing. This enables soft handoffs (FIGS. 27-29) to be handled in a manner transparent to the parties to the call and without significant involvement of system control elements (134 and 261 in FIG. 2) whose involvement would adversely impact the system's call-handling capacity. It also enables soft handoffs to occur without change of the call processing unit that is handling the call, so that a single call processing unit continues to handle the call from start to finish through even multiple soft handoffs.

Mobile telephone system call processing arrangement

A CDMA cellular radio-telephone system (FIG. 2) has switching systems (201) synchronized to public telephone network (100) timing signals (600), and radio telephones (203) and cell base stations (202) synchronized to a different clock (1000). Transmission delays between the cell base stations and the telephone network are variable. Switching systems include digital communications interfaces (264) to the telephone system, whose connections to the telephone system are synchronized to the telephone system, and whose connections to the cells are nominally also synchronized to the telephone system but whose processor (602) operates for each call within predefined windows (1302, 1402) of phase relationships to the operation of the cell that is handling the call, and occasionally adjusts (FIGS. 13-16) its phase relationships to the operation of the telephone system to achieve and maintain its operation within the predefined windows. Packet-switched communications (350) between the cells and the switching systems absorb the phase relationship fluctuations and the timing adjustments in inter-packet intervals. Circuit-switched signal communications between the switching systems and the telephone system absorb the timing adjustments by means of vocoder (604)-implemented slips--bit insertions or deletions--in the communications traffic bit stream.

Adaptive synchronization arrangement

A wireless-access communications system, such as a CDMA cellular radio-telephone system (FIG. 2), comprises a packet-switched communications network (202, 207, 201) that interconnects cells (base stations; 202) with each other and with the public telephone network (100). Traffic of individual calls is packetized, and packet-bearing frames (300 in FIG. 7) of a plurality of calls are then statistically multiplexed and frame-relayed through the network to yield the high capacity, efficiency, and speed of traffic transport and handoff required for a CDMA cellular system. At each call processing unit (264 in FIG. 5), individual calls are handled by individual service circuits (602 and 612) which perform speech-processing functions such as coding and decoding, tone insertion, and echo cancellation, and packet-to-circuit-switched-PCM traffic conversion. Processors (602) adapt call processing unit timing to compensate for asynchrony between cells and call processing units and variations in call path transmission delays. Cell-to-cell communications, fixed call path addressing, and packetized control message transfers ensure that the same service circuit handles a call through even multiple soft handoffs (FIGS. 27-29) and efficiently communicates simultaneously with all cells involved in the handoff without involvement of system control entities and negative effect on system call-handling capacity. Both coded (packet-switched) and uncoded (circuit-switched) radio-telephone traffic are accommodated side-by-side. Wherever possible, existing and proven technology and component units are used to achieve low cost and high reliability.

A CDMA cellular radio-telephone system (FIG. 2) has switching systems (201) synchronized to public telephone network (100) timing signals (600), and radio telephones (203) and cell base stations (202) synchronized to different clock (1000). Transmission delays between the cell base stations and the telephone network are variable. Switching systems include digital communications interfaces (264) to the telephone system, whose connections to the telephone system are synchronized to the telephone system, and whose connections to the cells are nominally also synchronized to the telephone system but whose processor (602) operates for each call within predefined windows (1302, 1402) of phase relationships to the operation of the cell that is handling the call, and occasionally adjusts (FIGS. 13-16) its phase relationships to the operation of the telephone system to achieve and maintain its operation within the predefined windows. Packet-switched communications (350) between the cells and the switching systems absorb the phase relationship fluctuations and the timing adjustments in inter-packet intervals. Circuit-switched digital communications between the switching systems and the telephone system absorb the timing adjustments by means of vocoder (604)-implemented slips--bit insertions or deletions--in the communications traffic bit stream.

A method and apparatus for decreasing delay and use of data processing resources in the reliable transmission of data frames in a packet network. In transmitting data from a source to a destination over a plurality of intermediate data switching points, the data processing required for each frame is selectively varied at each data switching point, according to the requirements for transmission of data frames of a message and of the succeeding link used for that message. A virtual link address is transmitted with each data frame which is translated into the mode of processing the frame at the data switching point, and into the virtual and real address of the next data link. Advantageously, such an arrangement allows for minimizing the data processing load and delay at each protocol handler of the data path through the packet network.

Fast packetized data delivery for digital networks

A PCM switching system requires the assignment of either one or two time slots of a pair of time slots to a port circuit depending upon the type of service (voice only or voice plus data) each port circuit provides. Common resources normally assign a pair of time slots to each port circuit. This wastes time slots when the port circuit is used in a manner (voice only service) that requires only a single time slot. The disclosed arrangement eliminates the wasting of time slots by permitting the on-site reconfiguring of the system resources so that, when desired, only a single time slot can be assigned to a port circuit. This is accomplished by the removal of a first type of carrier control board that controls time slot distribution and by the substitution therefore of a second type of control board that applies the first time slot of a pair to its normally assigned port circuit and applies the second time slot of the same pair to another port circuit on the same carrier that also only requires a single time slot. This permits a given system to be configured initially in a first mode and then be subsequently reconfigured on-site so the port circuits of a carrier can each be assigned either one or two time slots. This arrangement avoids the wasting of time slots or costly on-site modifications as service needs change.

Time slot assignment facilities

Apparatus for facilitating the transport and switching of synchronous and asynchronous digital data signals presented by data terminal or data communication equipments to a voice switching network such as a PBX advantageously without the use of modems. The clock rate of the PBX user's digital data is multiplied by a variable factor to define a synchronous transmission clock rate on a data link between a pair of interfaces, one locally connecting to the data terminal or data communications equipment and the other appearing as a port of the PBX switching equipment. The higher rate on the data link permits both the digital data as well as a control channel to be provided. Variations in the data terminal or data communications equipment clock rate do not affect the control channel. Variations in the voice sampling rate of switching modules serving different groups of ports through which the digital data is transported are accommodated.

Establishing and supporting data traffic in private branch exchanges

In a PAM bus switching bus which normally handles analog voice signals, the different DC offsets caused by the different buffing, summing and distribution amplifiers cause no ill effects because DC voltages are not passed by the remainder of the support elements. However, when it is attempted to switch logic level DC signals through such a PAM bus network, the DC offset which is an indeterminate function of the particular switching path established, makes it impossible to establish a uniform slicing level. In the illustrative embodiment a uniform slicing level is achieved by clamping the summing bus of the PAM system during a preamble of the time slot, measuring the offset on the distribution bus and then applying the measured offset to compensate the distribution bus during the remainder of the time slot when the actual data signal is allowed to be applied to the summing bus.

Growing community of inventors

Boulder, CO, United States of America

Douglas A Spencer